For instant messaging services, such as a voice service, a video service, and a short message service, an IP multimedia subsystem (IMS) can provide a user with high-quality IMS services that are based on a voice, a video, a short message service message, and the like. A service, such as a voice service, a video service, or a short message service, may be provided by using a user plane of an evolved packet system (EPS) network. For sending of user plane data, user equipment needs to first establish a radio resource control (RRC) connection to a network side, to change a status of the user equipment into a connection state. Establishment of the radio resource control connection includes initiating an access stratum (AS) signaling connection to an access network and initiating a non-access stratum (NAS) signaling connection to a core network.
Before establishing the RRC connection, the user equipment needs to determine, according to an access class barring (ACB) mechanism, whether there is access barring, so as to avoid excessively heavy cell load. According to a configuration policy of an operator, ACB may be skipped by broadcasting a service, such as a voice service, a video service, or a short message service, in an air interface system message by using the access network. In this way, after the user equipment reads and stores the system message, if a user initiates a service, such as a voice service, a video service, or a short message service, access control of current ACB may be skipped, to initiate a connection setup request to the access network for the service, such as a voice service, a video service, or a short message service. Specifically, an IMS layer of the user equipment notifies a type of a service initiated by the IMS layer to a NAS layer and an AS layer of the user equipment, and the AS layer determines, according to the type of the service initiated by the IMS layer, whether to skip access barring of the ACB.
In the foregoing technology, a final decision point of the ACB mechanism is at the AS layer of the user equipment. If the AS layer skips the ACB to initiate a signaling connection setup request, an access network side accepts the setup request. Based on this rule, the IMS layer of the user equipment needs to notify the type of the initiated service only to the NAS layer and the AS layer of the user equipment, to perform preferential access processing on the service, such as a voice service, a video service, or a short message service, on a user equipment side. However, from a perspective of the access network and the core network, when a signaling connection is being established, if the access network performs congestion control or overload control, the access network rejects a signaling connection request initiated by the user equipment, to relieve signaling load on the network side, that is, the network side rejects the signaling connection setup request when performing congestion control or overload control. Consequently, a service, such as a voice service, a video service, or a short message service, fails to be established.